Implications of the CDF <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mi>t</mml:mi><mml:mover accent="true"><mml:mi>t</mml:mi><mml:mo>¯</mml:mo></mml:mover></mml:math> forward–backward asymmetry for boosted top physics

Self Cite

The CDF collaboration has recently reported a large deviation from the standard model of the tt forward-backward asymmetry in the high invariant mass region. We interpret this measurement as coming from new physics at a heavy scale Λ , and perform a model-independent analysis up to O(1/Λ 4 ) . A simple formalism to test and constrain models of new physics is provided. We find that a large asymmetry cannot be accommodated by heavy new physics that does not interfere with the standard model. We show that a smoking gun test for the heavy new physics hypothesis is a significant deviation from the standard model prediction for the tt differential cross section at large invariant mass. At M tt > 1 TeV the cross section is predicted to be at least twice that of the SM at the Tevatron, and for M tt > 1.5 TeV at least three times larger than the SM at the LHC.

Section: Relevant Datamentioning

confidence: 99%

Section: Relevant Datamentioning

confidence: 99%

“…The cross section for ultra-massive boosted jets (not coming from QCD events) can be estimated as follows [42] …”

Section: Relevant Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Implications of the CDF $ t\bar{t} $ forward-backward asymmetry for hard top physics

Delaunay

Gedalia

Hochberg

et al. 2011

Self Cite

Measuring the bottom-quark forward-central asymmetry at the LHC

Kahawala

Krohn

Strassler

2012

Measurements of the top quark forward-backward asymmetry performed at the Tevatron suggest that new-physics may be playing a role in tt production. To better understand the source of the asymmetry, recent proposals have called for a measurement of the bottom and charm forwardbackward asymmetries at the Tevatron, using jets with embedded muons. Here we propose a corresponding measurement of the bottom quark forward-central asymmetry designed to look for similar effects in the b-sector at ATLAS and CMS. We construct a set of cuts designed to enhance sensitivity to this asymmetry, and test our analysis on a toy axigluon model representative of those used to explain the top asymmetry. We find that if the relevant new-physics couplings to the bottom quark are similar to those of the top, then the effects should be visible at the 2σ level in less than 10 fb −1 of 7 TeV LHC data. Such a measurement would be of general importance, and would provide valuable model-building input, serving to restrict the set of models put forward to explain the Tevatron tt anomaly. However, a relatively low trigger threshold on non-isolated muons inside hard jets must be maintained to allow for this measurement.

Search for resonances decaying into top-quark pairs using fully hadronic decays in pp collisions with ATLAS at $ \sqrt{s}=7 $ TeV

Aad¹,

Abajyan²,

Abbott³

et al. 2013

Abstract:A search for resonances produced in 7 TeV proton-proton collisions and decaying into top-quark pairs is described. In this Letter events where the top-quark decay produces two massive jets with large transverse momenta recorded with the ATLAS detector at the Large Hadron Collider are considered. Two techniques that rely on jet substructure are used to separate top-quark jets from those arising from light quarks and gluons. In addition, each massive jet is required to have evidence of an associated bottom-quark decay. The data are consistent with the Standard Model, and limits can be set on the production cross section times branching fraction of a Z boson and a Kaluza-Klein gluon resonance. These limits exclude, at the 95% credibility level, Z bosons with masses 0.70-1.00 TeV as well as 1.28-1.32 TeV and Kaluza-Klein gluons with masses 0.70-1.62 TeV. The ATLAS collaboration 34 IntroductionMany models of new phenomena beyond the Standard Model (SM) predict resonances in the TeV mass range that decay primarily into top-antitop quark pairs 1 (tt). This Letter reports on a search for such phenomena in proton-proton (pp) collisions at the Large Hadron Collider (LHC) where both top quarks are reconstructed in their fully hadronic final states and have large transverse momentum (p T ). The decay products of each high-p T top quark are collimated and merge into one jet with large invariant mass. Previous searches mostly considered cases where in one or both of the top-quark decays, the intermediate W boson decays leptonically and hence the top-quark decays result in one or two isolated leptons, missing energy from the neutrinos, and jets in the final state [1][2][3][4][5][6][7][8].The requirements of a well-identified charged lepton isolated from nearby hadronic energy deposits and missing transverse energy reject a large fraction of background from multijet production. However, difficulties arise in these final states when the top-quark decay 1 In the following "top quark" refers to both the top quark and its anti-particle.-1 - JHEP01(2013)116particles are collimated, since leptons from the top-quark decay are no longer isolated and thus background contributions with lepton candidates originating from hadronic jets are more difficult to distinguish from the signal.An alternative approach that is reported in this Letter is to consider final states with high-p T top quarks that decay hadronically and where the decay products are collimated in the direction of the top-quark. Such searches require the top quarks to have p T in excess of 200-300 GeV and require rejection of the large background of gluon jets, light-quark jets, as well as c-and b-jets. The CMS Collaboration employed this technique in a recent study [9].In the present analysis, two complementary algorithms are used to identify top-quark decays and reconstruct the top-quark momentum for data collected with the ATLAS detector at a centre-of-mass energy of 7 TeV. The first algorithm is the HEPTopTagger method [10, 11] that tests the substructure of a j...